Hulya Sarak - Academia.edu (original) (raw)

Papers by Hulya Sarak

Research paper thumbnail of The degree-day method to estimate the residential heating natural gas consumption in Turkey: a case study

Research paper thumbnail of A Trilinear Flow Model for a Fractured Horizontal Well in a Fractal Unconventional Reservoir

SPE Annual Technical Conference and Exhibition, 2014

Research paper thumbnail of ASSESSMENT OF UNCERTAINTY IN ESTIMATION OF STORED AND RECOVERABLE THERMAL ENERGY IN GEOTHERMAL RESERVOIRS BY VOLUMETRIC METHODS

In this paper, we investigate the propagation of uncertainties in the input variables (used in th... more In this paper, we investigate the propagation of uncertainties in the input variables (used in the volumetric method) on to stored and recoverable thermal energy estimates calculated from volumetric methods. Effects of the different types of input distributions, correlation among input variables and cognitive biases are also investigated. Both Monte Carlo (MC) and the analytic uncertainty propagation (AUP) methods are considered and compared for uncertainty characterization. Analytic uncertainty propagation equations (AUPEs) are derived based on a Taylor-series expansion around the mean values of the input variables. The AUPEs are general in that correlation among the input variables, if it exists, can also be accounted for on the resulting uncertainty. Monte Carlo methods (MCMs) were used to verify the results obtained from the AUPEs.

Research paper thumbnail of JEOTERMAL REZERVUARLARIN MODELLENMESİ

Research paper thumbnail of Lumped parameter reservoir models for low-temperature geothermal reservoirs

In this study, the production behavior of low-temperature geothermal reservoirs is simulated by a... more In this study, the production behavior of low-temperature geothermal reservoirs is simulated by analytical models. Models consider the effects of production and injection rates and natural recharge on the pressure or water level behavior of a low-temperature, liquid dominated geothermal reservoir. Reservoir and aquifer are represented by different tanks and the effect of recharge source is studied. Tank systems used

Research paper thumbnail of A NEW NON-ISOTHERMAL LUMPED-PARAMETER MODEL FOR LOW TEMPERATURE, LIQUID DOMINATED GEOTHERMAL RESERVOIRS AND ITS APPLICATIONS

We have developed a non-isothermal lumpedparameter model for predicting both pressure and tempera... more We have developed a non-isothermal lumpedparameter model for predicting both pressure and temperature behaviors of low temperature geothermal reservoirs containing a single-phase liquid water. Unlike the existing isothermal lumped-parameter models in the literature, the new model couples both energy (or heat) and mass balance equations and hence can be used to predict both temperature and pressure changes in the reservoir resulting from production of hot water, re-injection of a low temperature water into the system, and/or natural recharge. Variable production and re-injection rate histories are also handled. We have also developed an optimization code based on the Levenberg-Marquardt algorithm and coupled it with our new model to obtain a procedure for pressure and temperature data analysis.

Research paper thumbnail of ASSESSING UNCERTAINTY IN FUTURE PRESSURE CHANGES PREDICTED BY LUMPED-PARAMETER MODELS: A FIELD APPLICATION

Lumped parameter models provide an attractive alternative to numerical modeling of geothermal res... more Lumped parameter models provide an attractive alternative to numerical modeling of geothermal reservoirs with the distinct advantage of having to deal with fewer modeling parameters. Hence when such models are used, the aim of the modeling work is then to determine the parameters that best describe the system often through history matching. Once the parameters of the model are determined, we proceed to make future predictions under given production scenarios. However, throughout the modeling work, it is very important to asses the uncertainty that arises from (i) "measurement" errors or noise in observed data, (ii) modeling errors, (iii) nonlinear relationship between model parameters and observed response and (iv) non-uniqueness of the problem. Furthermore, it is crucial that this uncertainty be reflected to the future predictions. Hence instead of dealing with a single deterministic response, one can analyze various possible outcomes of the future predictions.

Research paper thumbnail of NEW LUMPED PARAMETER MODELS FOR SIMULATION OF LOW-TEMPERATURE GEOTHERMAL RESERVOIRS

A companion paper titled "New Lumped Parameter Models for Simulation of Low-Temperature Geotherma... more A companion paper titled "New Lumped Parameter Models for Simulation of Low-Temperature Geothermal Reservoirs" presents practical analytical models for simulation of low-temperature geothermal reservoirs. This paper deals with the applications of the new lumped-parameter models to field cases. The models are used to match the long-term observed water level or pressure response to a given production history. For history matching purposes, we use an optimization algorithm based on the Levenberg-Marquardt method to minimize an objective function based on weighted least-squares for estimating relevant aquifer/reservoir parameters. In addition, we constrain the parameters during nonlinear minimization process to keep them physically meaningful and compute statistics (e.g, standard 95% confidence intervals) to assess uncertainty in the estimated parameters. Three field examples taken from the literature are considered to show the use of the models and optimization algorithm. The observed and simulated water level changes obtained from the models are discussed. Results show a very good agreement between the observed field data and simulated data from the lumped models given in this work, in spite of long data sets.

Research paper thumbnail of Lumped-parameter models for low-temperature geothermal fields and their application

Geothermics, 2005

The behavior of low-temperature geothermal reservoirs under exploitation is simulated using analy... more The behavior of low-temperature geothermal reservoirs under exploitation is simulated using analytical lumped-parameter models. These models consider the effects of fluid production and reinjection, as well as natural recharge, on the pressures (or water levels) of low-temperature, liquid-dominated geothermal systems. The computed responses for constant production/injection flow rates are given in the form of analytical expressions. Variable flow rate cases are modeled, based on the Duhamel's principle. Reservoir parameters are obtained by applying a weighted nonlinear least-squares estimation technique in which measured field data are history matched to the corresponding model response. By using history-matched models, the future performance of the reservoir can be predicted for different production/injection scenarios in order to optimize the management of a given geothermal system.We demonstrate the applicability of the models by simulating measured data from the Laugarnes geothermal field in Iceland, and the Balcova–Narlidere field in Turkey.

Research paper thumbnail of The degree-day method to estimate the residential heating natural gas consumption in Turkey: a case study

Research paper thumbnail of A Trilinear Flow Model for a Fractured Horizontal Well in a Fractal Unconventional Reservoir

SPE Annual Technical Conference and Exhibition, 2014

Research paper thumbnail of ASSESSMENT OF UNCERTAINTY IN ESTIMATION OF STORED AND RECOVERABLE THERMAL ENERGY IN GEOTHERMAL RESERVOIRS BY VOLUMETRIC METHODS

In this paper, we investigate the propagation of uncertainties in the input variables (used in th... more In this paper, we investigate the propagation of uncertainties in the input variables (used in the volumetric method) on to stored and recoverable thermal energy estimates calculated from volumetric methods. Effects of the different types of input distributions, correlation among input variables and cognitive biases are also investigated. Both Monte Carlo (MC) and the analytic uncertainty propagation (AUP) methods are considered and compared for uncertainty characterization. Analytic uncertainty propagation equations (AUPEs) are derived based on a Taylor-series expansion around the mean values of the input variables. The AUPEs are general in that correlation among the input variables, if it exists, can also be accounted for on the resulting uncertainty. Monte Carlo methods (MCMs) were used to verify the results obtained from the AUPEs.

Research paper thumbnail of JEOTERMAL REZERVUARLARIN MODELLENMESİ

Research paper thumbnail of Lumped parameter reservoir models for low-temperature geothermal reservoirs

In this study, the production behavior of low-temperature geothermal reservoirs is simulated by a... more In this study, the production behavior of low-temperature geothermal reservoirs is simulated by analytical models. Models consider the effects of production and injection rates and natural recharge on the pressure or water level behavior of a low-temperature, liquid dominated geothermal reservoir. Reservoir and aquifer are represented by different tanks and the effect of recharge source is studied. Tank systems used

Research paper thumbnail of A NEW NON-ISOTHERMAL LUMPED-PARAMETER MODEL FOR LOW TEMPERATURE, LIQUID DOMINATED GEOTHERMAL RESERVOIRS AND ITS APPLICATIONS

We have developed a non-isothermal lumpedparameter model for predicting both pressure and tempera... more We have developed a non-isothermal lumpedparameter model for predicting both pressure and temperature behaviors of low temperature geothermal reservoirs containing a single-phase liquid water. Unlike the existing isothermal lumped-parameter models in the literature, the new model couples both energy (or heat) and mass balance equations and hence can be used to predict both temperature and pressure changes in the reservoir resulting from production of hot water, re-injection of a low temperature water into the system, and/or natural recharge. Variable production and re-injection rate histories are also handled. We have also developed an optimization code based on the Levenberg-Marquardt algorithm and coupled it with our new model to obtain a procedure for pressure and temperature data analysis.

Research paper thumbnail of ASSESSING UNCERTAINTY IN FUTURE PRESSURE CHANGES PREDICTED BY LUMPED-PARAMETER MODELS: A FIELD APPLICATION

Lumped parameter models provide an attractive alternative to numerical modeling of geothermal res... more Lumped parameter models provide an attractive alternative to numerical modeling of geothermal reservoirs with the distinct advantage of having to deal with fewer modeling parameters. Hence when such models are used, the aim of the modeling work is then to determine the parameters that best describe the system often through history matching. Once the parameters of the model are determined, we proceed to make future predictions under given production scenarios. However, throughout the modeling work, it is very important to asses the uncertainty that arises from (i) "measurement" errors or noise in observed data, (ii) modeling errors, (iii) nonlinear relationship between model parameters and observed response and (iv) non-uniqueness of the problem. Furthermore, it is crucial that this uncertainty be reflected to the future predictions. Hence instead of dealing with a single deterministic response, one can analyze various possible outcomes of the future predictions.

Research paper thumbnail of NEW LUMPED PARAMETER MODELS FOR SIMULATION OF LOW-TEMPERATURE GEOTHERMAL RESERVOIRS

A companion paper titled "New Lumped Parameter Models for Simulation of Low-Temperature Geotherma... more A companion paper titled "New Lumped Parameter Models for Simulation of Low-Temperature Geothermal Reservoirs" presents practical analytical models for simulation of low-temperature geothermal reservoirs. This paper deals with the applications of the new lumped-parameter models to field cases. The models are used to match the long-term observed water level or pressure response to a given production history. For history matching purposes, we use an optimization algorithm based on the Levenberg-Marquardt method to minimize an objective function based on weighted least-squares for estimating relevant aquifer/reservoir parameters. In addition, we constrain the parameters during nonlinear minimization process to keep them physically meaningful and compute statistics (e.g, standard 95% confidence intervals) to assess uncertainty in the estimated parameters. Three field examples taken from the literature are considered to show the use of the models and optimization algorithm. The observed and simulated water level changes obtained from the models are discussed. Results show a very good agreement between the observed field data and simulated data from the lumped models given in this work, in spite of long data sets.

Research paper thumbnail of Lumped-parameter models for low-temperature geothermal fields and their application

Geothermics, 2005

The behavior of low-temperature geothermal reservoirs under exploitation is simulated using analy... more The behavior of low-temperature geothermal reservoirs under exploitation is simulated using analytical lumped-parameter models. These models consider the effects of fluid production and reinjection, as well as natural recharge, on the pressures (or water levels) of low-temperature, liquid-dominated geothermal systems. The computed responses for constant production/injection flow rates are given in the form of analytical expressions. Variable flow rate cases are modeled, based on the Duhamel's principle. Reservoir parameters are obtained by applying a weighted nonlinear least-squares estimation technique in which measured field data are history matched to the corresponding model response. By using history-matched models, the future performance of the reservoir can be predicted for different production/injection scenarios in order to optimize the management of a given geothermal system.We demonstrate the applicability of the models by simulating measured data from the Laugarnes geothermal field in Iceland, and the Balcova–Narlidere field in Turkey.